The estimated number of liverwort species range from 7,500 to 9,000.
Traditionally, liverworts have been subdivided into two major groups or
classes based, partially, on growth form. The class Marchantiopsida,
includes the well-known genera
Marchantia,
Monoclea,
Lunularia,
and
Riccia,
and has a complex thalloid organisation. The class Jungermanniopsida
represents an estimated 85% of liverwort species and shows an enormous
amount of morphological, anatomical and ecological diversity; plants with
leafy shoot systems are the most common growth form in this class, e.g.,
Frullania,
Jubulopsis,
Cololejeunea,
and
Radula.

Liverworts are pivotal in our understanding of early land plant evolution.
A growing body of evidence supports liverworts as the earliest diverging lineage of embryophytes.
Liverworts form both a conspicuous and important component in many ecosystems throughout the world,
responding rapidly to environmental change, and therefore are of ecological significance in many biotic systems.

Studies of terrestrial global diversity patterns based on quantitative data have been confined to vascular plants and animals,
and more recently, macro-fungi. We here present the first preliminary data set recording the distribution of liverwort species
across 368 geo-political units based on 50,000 records from over 250 published and unpublished checklists and papers.

The data set contains over 7500 valid species names.
This figure may not be representative of the global species richness of hepatics,
however, which is possibly much lower taken into consideration the complex synonymy in many taxa,
the large number of unrevised genera and families, and the quality of the underlying data.
This database is the most comprehensive catalogue of liverwort species worldwide,
and makes significant steps toward the compilation of a worldwide checklist of liverworts.

The development of such a checklist has far reaching implications and applications,
including global mapping of species richness; comparative studies between liverwort
phytogeographic patterns with existing floristic regions and conservation hotspots
as defined by vascular plants, animals, and fungi; and assessing the state of floristic
knowledge and identifying geographical gaps in our understanding of the global liverwort flora.
Although there are many challenges ahead to obtain high quality data,
quantifying global liverwort diversity is a tractable, multi-faceted and scientifically important goal,
and everyone stands to gain by fostering this endeavour. The success of the project will lie on strong
collaborative between institutions and the bryological community in general.